Transcript

2.
Lecture Aims• To introduce the mechanical concept of lower extremity stiffness and methods of calculation• To examine how lower extremity stiffness is regulated during dynamic movements• To discuss the influence of lower extremity stiffness on functional performance• To explain the affect of static stretching, training and coaching cues on lower extremity stiffness

3.
What is Stiffness?• Stiffness describes the relationship between a given force and the deformation of an object or body (Butler et al., 2003; Brughelli and Cronin, 2008a)• Hooke’s Law: F = kx rearranged to k = ∆F ∆x• The spring constant (k) describes the stiffness of an ideal spring-mass-system

12.
Tendon Stiffness (Kten) (Hopping)Tendon stiffness (N·mm-1) isdetermined from the slopeof the elongation – forcerelationship The same method is used to calculate muscle fibre, muscle and MTU stiffness

36.
Tendon Training SummaryFor increases in tendon stiffness to occur, trainingshould:• Include high loads (>70% 1RM)• Involve high tendon strains (↑ drop heights)• If isometric, be performed at long muscle lengths• If isometric, be performed for at least 3s/rep• Be performed consistently for at least 6-8 weeks

37.
Kleg & Kjoint Training SummaryFor increases in Kleg & Kjoint to occur, training should:• Include high loads (>75% 1RM)• Involve large muscle mass (Squats/Deadlifts)• Include both strength and power exercises• Be task specific• Be performed when technically competent• Be monitored to avoid excessive recruitment

38.
Training Proposal• Strength training and low-intensity plyometrics (coached correctly) should proceed high-intensity plyometric performance (for at least 6-8 weeks) in order develop necessary Kten to help avoid excessive tendon strains that may lead to injury.• Plyometric training drills should be specific to the lower extremity stiffness characteristics of each athletes’ sport in order to enhance their transferability to performance.